1. Field of the Invention
This invention relates to methods and systems for manufacturing and assembling, and, in particular, to methods and systems for manufacturing and assembling computer systems in a build-to-order environment.
2. Description of the Related Art
Traditionally, manufacturing systems have been designed and constructed based upon a build-to-stock model where large quantities of identical products are assembled to meet forecasted demand and warehoused until that demand occurs. Such manufacturing systems provide economies of scale based upon the large quantities of identical units and can be optimized by increasing the speed with which each manufacturing step is completed. Because build-to-stock manufacturing systems rely on known product configurations, each step in the manufacturing process is known in advance, and so the manufacturing system utilizes progressive build techniques to optimize each stage in the serial assembly process. For products (e.g. a computer system) that include sensitive components, progressive build manufacturing systems can be carefully planned in advance to protect those sensitive components. Once the manufacturing system becomes operational, it will build the same product repeatedly, using the optimized steps.
However, when the process is adapted to build a different product, or a different version of the same product, the manufacturing system must be modified and re-optimized to ensure that the system still protects sensitive components. Moreover, because the progressive build process is serial, each stage depends on timely completion of the previous stage, and thus the entire process is susceptible to problems, inefficiencies, and failures in any of the stages of the system. Additionally, progressive-build manufacturing systems operating in a build-to-stock environment are relatively inflexible, limiting the ability of the manufacturing system to fill small orders economically and to control inventory.
One method used to increase performance in progressive-build manufacturing processes is to include a process step in which identical kits are prepared that hold the components needed to assemble a particular product or to complete a particular manufacturing step. In this way some of the time normally required to select parts for a particular product or manufacturing step can be reduced, and some manufacturing steps can more easily be performed in one location or by one operator or piece of manufacturing equipment (e.g. an industrial robot). For example, U.S. Pat. No. 4,815,190 discloses the use of automated and manual kitting stages for producing identical kits for automobile sub-assemblies. One advantage to using identical kits is that it is relatively easy to know if all of the parts needed to assemble a particular product are present in the kit; a missing part stands out because each kit should always have the same set of components.
As an alternative to progressive-build manufacturing systems which are often faced with the problem of large dwell times, i.e. time periods where a product being assembled must wait before moving to a subsequent assembly stage, some manufacturing systems have been shifted to continuous flow manufacturing (CFM) methods. In general, CFM methods employ a demand-driven pull system for inventory control and movement of components into the assembly process. This can include the use of kanban techniques for inventory control and movement. CFM also supports mixed-model manufacturing continuous flow production lines. CFM systems offer continuous flow of value added activities, eliminating wasted motion and dwell times. Other terms often used for CFM include Just-In-Time (JIT) manufacturing, Flexible and Agile Manufacturing, Synchronous Manufacturing and Demand Based Conversion.
Personal computers, servers, workstations, portables, embedded systems and other computer systems are typically assembled in manufacturing systems designed for build-to-stock environments. A typical personal computer system includes a processor, associated memory and control logic and a number of peripheral devices that provide input and output (I/O) for the system. Such peripheral devices include, for example, compact disk read-only memory (CD-ROM) drives, hard disk drives, floppy disk drives, and other mass storage devices such as tape drives, compact disk recordable (CD-R) drives or digital video/versatile disk (DVD) drives.
Manufacturing computer systems becomes inefficient when the number of identical units is decreased and process steps are changed as orders change, both of which are characteristics of a build-to-order environment where computer systems (or products generally) are manufactured or assembled only after an order for that particular computer system has been placed. As a result, the conventional manufacturing systems do not adapt well to the build-to-order environment and can limit the ability to fill small orders, require extra inventory, generate more work-in-process, and be globally constrained by the slowest process step. This process also requires line changeovers and new tooling when change is required. One attempt to adapt and to improve the efficiency of conventional manufacturing systems has been to reduce the number of components prepared in advance of orders. By limiting such in-process inventory, the line can change configurations more easily as orders change. However, this scheme is still limited in its efficiency for smaller orders in the build-to-order environment.
Because computer systems manufacturers have recognized that a build-to-order environment is advantageous and often can better react to the speed with which product designs and customer expectations change, there is a need to provide manufacturing systems and methods that more efficiently integrate with the build-to-order model while ensuring that high quality, defect free products are produced.